He is accused of filing approximately $4 million worth of fraudulent tax returns starting in 2005. The FBI used a device called a "stingray" to catch Rigmaiden. It's able to track down a cell phone's location so long as it's powered "on."

The device acts like a cellphone tower. It "pings" the phone and measures the resulting signals. It has uses beyond apprehending suspected criminals. It can also be used in search and rescue attempts. And it's only sold to government and law enforcement.

It seems that the FBI obtained a court order -- but not a search warrant. And it appears that one of the prosecution's vital arguments is that a search warrant isn't necessary. They assert that Rigmaiden has no standing to bring a Fourth Amendment claim because he used a fake name when he purchased the broadband card and service. Furthermore, he used a false name to rent out his apartment.

In short, he has no reasonable expectation of privacy.

But The Wall Street Journal has pointed out these contentions may not stand. After all, courts in other cases have upheld an individual's privacy rights when they use a false name.

The FBI's use of the stingray device may face further scrutiny. The data is actually deleted off the device. It's not returned to a judge. A criminal defendant also cannot access the information because the information has already been wiped.

Should buying a phone with a fake name reduce your right to privacy? That's the question the federal court may have to weigh in on.